At least some 2-alkoxy-estra-3,17.beta.-diols (hereinafter "2-alkoxy estradiols") have anticancer activity. For example, when tested in mice, 2-methoxy estradiol (1) acts as a potent inhibitor of neovascularization of solid tumors and inhibits their growth at doses which produce no apparent signs of toxicity (Fotsis et al., Nature 368:237 (1994). 2-Methoxy estradiol (1) is thought to inhibit tumor growth act by: 1) inhibiting DNA synthesis and mitosis (Breuer et al., Naturwissenschaft 12:280 (1960) and Gelbke et al., J. Steroid Biochem, 7:457 (1976) ); 2) inhibiting tubulin polymerization or causing the formation of tubulin polymer with altered morphology and stability properties (D'Amato et al., Proc. Natl. Acad. Sci. U.S.A. ##STR2## 91:3964 (1994)); or 3) inhibiting angiogenesis, i.e. the creation of new blood vessels required for the growth of solid tumors (Fotsis et al., Nature 368:237 (1994), Folkman et al., Nature 339:58 (1994) and Blood et al., Biochim. Biophys. Acts et al., 1032:89 (1990)).
2-Alkoxy estradiols are estrogen analogs and are therefore expected to have affinity for the estrogen receptor. This could complicate their use as anticaner agents. Thus, there is also a need for new 2-alkoxy estradiols and analogs thereof with improved activity compared with 2-methoxy estradiol (1) and with reduced affinity for the estrogen receptor.